It is common to support medium to high voltage (e.g., greater than 2K volts) cables on wooden poles supported by ceramic insulators. Frequently, there are three parallel cables, each carrying a different phase. If there is a short to ground or a short between cables, a fuse or breaker will trip, causing a power outage or a rerouting of the electricity. A lineman must then fix the problem and reset the fuse/breaker.
FIG. 1 is a perspective view of a conventional ceramic insulator 10 that is mounted on a wooden pole (not shown) using conventional hardware, such as a bracket or a bolt. Round insulators are typically 4-8 inches in diameter. A bare cable 12 is secured to the insulator 10 by a wire (not shown) twisted around the insulator neck 13 and the cable 12. FIG. 2 is a top down view of the insulator 10 and cable 12. For three phase distribution, there are typically two insulators/cables at the ends of a wooden cross-arm and one insulator/cable supported in the middle or on the top of the pole.
When there is a straight run of the cable 12, the cable 12 may be supported by the indent 14 at the top of the insulator 10 or may be tied to the side of the neck 13. A twist wire keeps the cable 12 in place. When the cable path needs to change direction, the cable 12 is bent around the neck 13 of the insulator 10, as shown in FIGS. 1 and 2. If the cable 12 is supported by the indent 14, for a straight run, the structure is symmetrical. If the cable 12 is tied to the side of the neck 13, as shown in FIGS. 1 and 2, the structure is asymmetrical.
In locations where there are trees, large birds, other animals, or the voltage is particularly high, cable shields are sometimes used to prevent arcing by a tree or an animal when the tree or animal contacts two or more of the phased cables. It is common to only put the shield over the center insulator/cable. Such shields are formed of a plastic, which may be resilient or rigid.
Shields that simply cover a straight cable 12 supported by the top indent 14 of the insulator 10 are simple and adequate, since the insulator/cable structure is symmetrical.
Shields are known that have two arms extending from a wide central portion of the shield that covers the ceramic insulator, where the arms cover the cable extending in both directions. The shield is formed of a soft, resilient plastic, and the arms can bend at different angles relative to the central portion. One such shield is the Tyco Electronics Corporation BCIC-G-PIN-795 raptor guard, whose arms flex up to 30 degrees.
One problem with the BCIC-G-PIN-795 shield is that it assumes the cable 12 is supported symmetrically at the center of the insulator 10 within the indent 14. However, if the cable 12 is bent around the neck 13 of the insulator 10, the insulator/cable is not symmetrical, and the shield will not properly fit over the insulator 10 and cable 12. As a result, the resilient shield material will be angled and distorted. This reduces the effectiveness of the shield and is not aesthetically pleasing. An angled shield opens up the underside of the shield to the wind, placing a large strain on the shield.
What is needed is a universal shield for cables supported by insulators, where the shield precisely adapts, without any distortion, to the asymmetrical arrangement of a cable 12 bent around the neck 13 of the insulator 10, as well as when the cable 12 is supported by the indent 14 at the top of the insulator 10.